During Monday's Blinds, Ariana said that John "pushed a button, literally and figuratively" when he blocked her to land showtune-loving crooner Joshua Vacanti last week. She was ready for payback, but unfortunately, she was a little slow on the draw.
When Samara Brown, a singer from The Bronx -- who is actually the sister of season 3 Voice contestant Amanda Brown -- took the stage for her audition, she wowed the coaches immediately with her rendition of Chaka Khan's "Sweet Thing." Ariana went for the block, but John was quicker, hitting his button first and preventing Ari from blocking him.
"I tried so hard to block him!" Ariana told Samara as the coaches made their bids to land the talented singer. "I hit it 30 times, I was one second too late!"
"Sometimes, when the devil's trying to do his work, the lord steps in," John celebrated, telling Samara, "You killed it...I would love to work with you, as much as someone tried to stop that from happening."
Ultimately, the failed block came back to bite, as Samara made the choice to join Team Legend.
"Ariana tried so hard to block me, but she was just a second too late," John told the cameras after his big win. "My trigger finger's been extra quick today, because I know the block is coming."
Ultimately, Ari did get John back, blocking him on the last singer of the night, an impressive four-chair turn performance from Kentucky native Holly Forbes, who wowed the coaches with her performance of Elton John's "Rocket Man."
"I made it by a millisecond, and I am so happy!" Ariana said of blocking John, who sarcastically agreed that he was also happy for her.
ET spoke with the Voice coaches during their season 21 press conference ahead of the premiere, where John, Kelly and Blake placed the target squarely on Ariana's back as the first-time coach this season -- especially because so many of the show's young singers idolize the two-time GRAMMY winner's vocal talent and chart success.
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"Of course she's a threat!" John said with a laugh. "She is hugely talented, hugely successful and has legions and legions of fans that know how to use the internet and vote."
"There's no disadvantage when you're Ariana Grande," Kelly agreed. "She can't say it. I will."
"It's embarrassing to follow her [onto the Voice stage]," Blake joked of the audience's enthusiasm for the "7 Rings" singer. "It exposes my lack of celebrity."
As a longtime "huge fan of The Voice," Ariana was humble about her possible advantages, but said she couldn't wait for fans to see how her season 21 team comes together.
"I have watched many seasons and I love watching the show," she said. "It always has the best energy. It's such wholesome, inspiring television, and I love seeing the different voices and watching so many people start careers for themselves. It's a beautiful, amazing thing."
The Voice airs Mondays and Tuesdays at 8 p.m. PT/ET on NBC. See more from this season in the video below.